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感谢您点击此主题以获取代码和反馈。Swift iOS9 - dispatch_group - 需要按特定顺序执行的代码
我的代码没有按预期工作。我需要代码按照输入的顺序进行操作。目前只有前两个部分按需要工作。 查看代码中的注释以获取更多详细信息。
tl; dr我如何让注释部分按照输入注释的顺序执行？
func getResults() {
resultsFollowingArray.removeAll(keepCapacity: false)
resultsDisplayNameArray.removeAll(keepCapacity: false)
resultsProfilePicArray.removeAll(keepCapacity: false)
resultsNoticeReasonArray.removeAll(keepCapacity: false)
resultsNoticeDescriptionArray.removeAll(keepCapacity: false)
resultsDatePostedArray.removeAll(keepCapacity: false)
let followGroup: dispatch_group_t = dispatch_group_create()
let profilePicGroup: dispatch_group_t = dispatch_group_create()
let noticesGroup: dispatch_group_t = dispatch_group_create()
/*** needs to execute first ***/
dispatch_group_async(followGroup, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
let fQ = PFQuery(className: "Following")
fQ.limit = 30
fQ.whereKey("follower", equalTo: myEmail)
do {
let objs = try fQ.findObjects()
for obj in objs {
self.resultsFollowingArray.append(obj.valueForKey("followed") as! String)
}
print(self.resultsFollowingArray) //works fine
} catch _ {
}
})
/*** needs to execute second ***/
dispatch_group_notify(followGroup, dispatch_get_main_queue(), {
if (self.resultsFollowingArray.count > 0) {
dispatch_group_async(profilePicGroup, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
let uQ = PFQuery(className: "_User")
uQ.limit = 30
for (var i = 0; i < self.resultsFollowingArray.count; i++) {
uQ.whereKey("username", equalTo: self.resultsFollowingArray[i])
do {
try self.resultsProfilePicArray.append(uQ.getFirstObject().valueForKey("profile_picture") as! PFFile)
} catch _ {
}
}
print(self.resultsProfilePicArray) //works fine
})
}
})
/*** needs to execute third ***/
/*** this section seems to be the first section to execute, therefore it is not working as I need it ***/
dispatch_group_notify(profilePicGroup, dispatch_get_main_queue(), {
print(self.resultsFollowingArray) //prints empty array
if (self.resultsFollowingArray.count > 0) {
dispatch_group_async(noticesGroup, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), {
let nQ = PFQuery(className: "Notices")
nQ.limit = 30
for (var i = 0; i < self.resultsFollowingArray.count; i++) {
nQ.whereKey("poster", equalTo: self.resultsFollowingArray[i])
do {
let notices = try nQ.findObjects()
for notice in notices {
self.resultsDisplayNameArray.append(notice.valueForKey("poster_display_name") as! String)
self.resultsNoticeReasonArray.append(notice.valueForKey("reason") as! String)
self.resultsNoticeDescriptionArray.append(notice.valueForKey("notice_description") as! String)
self.resultsDatePostedArray.append(notice.valueForKey("date_posted") as! String)
}
self.tvMyFeed.reloadData()
print(self.resultsDisplayNameArray) //prints nothing
} catch _ {
}
}
})
}
})
/*** needs to execute last ***/
dispatch_group_notify(noticesGroup, dispatch_get_main_queue(), {
self.tvMyFeed.reloadData()
})
}
更新后的代码：出于某种奇怪的原因，PFQuery“Notices”被调用了两次，它将所有东西都搞砸了。这是我想要做的，但我试图做到“在后台”，这段代码仍冻结了用户界面：
let group: dispatch_group_t = dispatch_group_create()
dispatch_group_enter(group)
let fQ = PFQuery(className: "Following")
fQ.limit = 30
fQ.whereKey("follower", equalTo: myEmail)
do {
let objs = try fQ.findObjects()
for obj in objs {
self.resultsFollowingArray.append(obj.valueForKey("followed") as! String)
}
dispatch_group_leave(group)
} catch _ {
dispatch_group_leave(group)
}
dispatch_group_enter(group)
let uQ = PFQuery(className: "_User")
uQ.limit = 30
for (var i = 0; i < self.resultsFollowingArray.count; i++) {
uQ.whereKey("username", equalTo: self.resultsFollowingArray[i])
do {
try self.resultsProfilePicArray.append(uQ.getFirstObject().valueForKey("profile_picture") as! PFFile)
} catch _ {
dispatch_group_leave(group)
}
}
dispatch_group_leave(group)
dispatch_group_enter(group)
let nQ = PFQuery(className: "Notices")
nQ.limit = 30
for (var i = 0; i < self.resultsFollowingArray.count; i++) {
nQ.whereKey("poster", equalTo: self.resultsFollowingArray[i])
do {
let notices = try nQ.findObjects()
for notice in notices {
self.resultsDisplayNameArray.append(notice.valueForKey("poster_display_name") as! String)
self.resultsNoticeReasonArray.append(notice.valueForKey("reason") as! String)
self.resultsNoticeDescriptionArray.append(notice.valueForKey("notice_description") as! String)
self.resultsDatePostedArray.append(notice.valueForKey("date_posted") as! String)
}
dispatch_group_leave(group)
} catch _ {
dispatch_group_leave(group)
}
}
dispatch_group_notify(group, dispatch_get_main_queue(), {
self.tvMyFeed.reloadData()
})